During bone scan what would cause mild radiotracer increase in si joints and mid feet?

Spondyloartopathy: The spondyloarthropathies (spinal based arthritis) have in common sacroileitis and other joint arthritis. It occurs in a wide diversity of disorders, i.e., anklylosing spondylilitis , reiters enthesopathy, psoriatic arthritis, ulcerative colitis, juvenile arthritis-you may not have any of these, just a mild form , but yearly follow-up with your doctor and reporting new symptoms is in order.